PRODUCTIVITY AND ECOLOGICAL FEATUES OF PURE PINE STANDS AND MIXED PINE STANDS WITH BLACK ALDER

Abstract

This study assesses the productivity and structural characteristics of pure Scots pine (Pinus sylvestris L.) stands and mixed Scots pine–black alder (Alnus glutinosa (L.)) stands growing in nutrient-poor forest sites in southern Lithuania. The mixed stands were established 40–60 years ago following the afforestation concept proposed by A. Olšauskas, aimed at improving soil fertility and forest productivity. The research was conducted in forest stands located in the Kapčiamiestis forestry of the Druskininkai regional unit of the State Forestry Enterprise. Field measurements in sample plots included diameter at breast height, tree height, stand density and stand volume. Comparative analysis revealed differences between pure pine stands and mixed pine–black alder stands. The results indicate that the presence of black alder improves nutrient cycling and creates more favorable conditions for Scots pine growth. Mixed stands also show greater structural diversity and higher ecological stability. The findings support species mixing as a sustainable forest management approach in nutrient-poor pine forest sites.